The present invention relates to an energy dispersive X-ray spectrometer (hereinbelow abbreviated to EDS), and in particular to an energy dispersive X-ray spectrometer used by combining it with an electron microscope such as a transmission electron microscope, a scanning electron microscope, an electron probe microanalyzer, etc.
Heretofore the EDS is used often by combining it with an electron microscope (including a transmission electron microscope, a scanning electron microscope, etc.) and utilized for element analysis of a specimen or sample image observed by using an electron microscope. This element analysis can be classified roughly into the qualitive analysis, by which what elements are contained is studied, and the quantitative analysis, by which what elements are contained and how much they are contained are studied. The qualitative analysis can be effected relatively easily, because the elements are only identified on the basis of the position of peaks in a spectrum. On the contrary, the quantitative analysis cannot be effected always easily, because the quantity thereof is calculated by substituting parameters in complicated formulas including various factors by experimental values obtained under different conditions and therefore various factors are entangled therein. The EDS analysis executed by combining it with an electron microscope is described in "Scanning Electron Microanalyzer and X-ray Microanalysis" edited by Joseph I. Goldstein, et al., 1981, pp. 222-273.
As an important cause producing analysis errors in the prior art techniques described above, in particularly in the quantitative analysis, it can be cited that errors in the energy of the electron beam, with which the sample is irradiated, are great. This occurs by the fact that the value set for the acceleration voltage on the EM side is used for the EDS analysis as it is. That is, formulas including various parameters are used for the quantitative EDS analysis and the set value of the acceleration voltage for the electron beam used in the electron microscope is used as one of the parameters in this formulas. Although the acceleration voltage is set at a certain value, e.g. 100 kV, because of errors in the adjustment of the EM device, the acceleration voltage of the electron beam used for the irradiation is not always 100.00 kV. For example, for an electron microscope it is 100.23 kV and for another it is 99.88 kV. For this reason, heretofore there was a problem that since the set value, which is no real acceleration voltage, is substituted in the formulas stated above as the acceleration voltage, errors are produced in the result of the quantitative analysis.